DoE and inputting replicate analytics

Question

Hi,

I have performed a DoE as designed, but would like to know how to evaluate replicate analytical data which feeds into the response for each condition.

We usually use analytical data provided by our analytical department, but are investigating a rapid analysis tool for future applications. While this tool is helpful, it appears most accurate when performing replicate analysis, and then averaging to achieve the mean. Typically, we manually (and by judgment call) will remove outlier response data, but I was hoping this data could be input into the JMP DoE platform, and it would automatically determine outliers.

How do I input this replicate data, but avoid JMP believing these are true replicates, and not simply replicate analysis of the same condition? If I don't, I assume JMP will provide an "Overly confident" profile, unless I am misunderstanding something.

GregF_JMP · Answer

Hello MetalLizard...

I appreciate your initial instinct to ask the question- repeated measure of the same experimental run are different than a "fresh" repeat of the iteration that encompasses all sources of variability: starting materials, adherence to factor settings etc.  I concur with the previous community input on this.

Your initial question was two part: repeated measure averaging/outlier detection & exclusion as part of measuring responses in a DOE.

JMP can help with both parts, but addressed individually.

I also agree with the other community members suggestions, my instinct would also be to aggregate in a separate data table, then summarize.

While the savings in time/cost with the "rapid measurement system (prone to outliers, that can be manually identified and excluded)" vs use of "analytical department measures" might be a great choice for your situation - there are a few caveats.
These two measurement systems might give net results that have an offset, slope or linearity difference.

JMP also has great tools for measurement systems evaluation.

* If the goal of the experiment is to determine the factor settings that will maximize or minimize a response, any difference in measurement systems will probably not matter.

*But*

* If the goal is to determine the factor settings to hit a certain target (as measured by analytic dept)... or
* if there is a specification limit for the response (again "as measured by analytical dept") that needs to be avoided as part of factor operating range establishment... or
* if the goal is to build (and publish) a model to predict outcomes, given future set of factor settings (for input X's, we expect what value of Y)

.....then a means to translate between measurement systems becomes more relevant.

Regarding outlier detection/exclusion

JMP has a variety of tools that support this effort.  Do they make the exact same decisions as your "manually/by judgment call"...  "it depends".  The suggest architectures of summarizing multiple rows will work, with a step where outlier rows have been reviewed and selectively excluded.  There also could be some outlier screening put into column formulas that would selectively exclude (conditional "missing") rows deemed unusual.

MRB3855 · Answer

Hi @MetaLizard62080 : Another option would be to stack the data as you describe; then, along with the other fixed factors in your DoE, include "run" as a random effect in your model. The results will be the same as analyzing the means (as @gonzaef and @Steffen_Bugge  suggested), but you'll get the additional information about run-to-run variability, and within-run variability.

Edit: How many design factors are in your DoE?

gonzaef · Answer

building on what have already being commented,

I believe you are doing repeats (repeated measurements, which do not add degrees of freedom) not replicates (independent events, meaning redoing the setup of factor in each run, which add degrees of freedom).

What I would do is to summarize the 120 rows table taking the average of your each of your treatments ending up with a table with only 12 rows (each row represents the average of 10 measurements) and use this table to fit your model.

You can use the average to look for factor which may be active to control the mean position (location factors) and storing also any dispersion metric (range, std dev or variance), usually log transformed, you can build another model to look for factors that may be active to reduce the process dispersion (dispersion factors).

Please let me know if you need any clarification,